Abstract
Studies on short-term memory have repeatedly demonstrated the beneficial effect of semantic similarity. Although the effect seems robust, the aspects of semantics targeted by these studies (e.g., categorical structure, associative relationship, or dimension of meaning) should be clarified. A recent meta-regression study inspired by Osgood's view, which highlights affective dimensions in semantics, introduced a novel index for quantifying semantic similarity using affective values. Building on the results of the meta-regression of past studies' data with that index, this study predicts that semantic similarity is deleterious to short-term memory if it is manipulated by affective dimensions, after controlling for other confounding factors. This prediction was directly tested. The experimental results of the immediate serial recall task (Study 1) and immediate serial reconstruction of order task (Study 2) indicated null effects of semantic similarity by affective dimensions and thus falsified the prediction. These results suggest that semantic similarity based on affective dimensions is negligible.